Seminar 3

COMP122 Seminars 2021-02-24

Division by Zero in Java

Generally, will give no error and the result Infinity.

If you divide 0.0 by 0.0 then you will get the result NaN.

Code Blocks

Indentation is ignored by the compiler. You should use {} to properly define your blocks.

switch statements

This can we used as a case select statement.

switch (x) {
	case 0:
	case 1: // code to run
		break; // this will have it stop after the block.
	default: //default code to run
		break;
}

The break reserved word ceases execution of the switch block. The default case is not required.

Inherits from C/C++

int a = 0;
int b = 0;

int c = 12 > 10 ? ++a : b++;	// the ? can be used in place of an if

If the condition before ? is true then the first condition is executed. If false then the condition after : is executed.

To increment numbers ++ can be used. There can be two cases:

• a++
  • This evaluates to the old value of a but increments a.
• ++a
  • This evaluates to the increment of a and increments a.

A Random Walk Example

Generating a Random Value of 1/-1

Math.random() gives a decimal number in the range $0\leq x<1$.

You can use Math.floor(x) to concatenate to integer.

Math.floor(Math.random()) will give 0 or 1 randomly.

Assessment 1

This assessment is based around the Caesar Cipher.